The present invention relates to proteins belonging to a novel class of proteins designated as xcex2-expansins, a composition comprising such proteins, isolated polynucleotides encoding xcex2-expansins, methods for using the polynucleotides and proteins of the invention and methods for identifying, isolating and purifying expansins, including xcex1 and xcex2-expansins.
Many grasses, such as rye grass, Kentucky bluegrass and orchard grass, release prodigious quantities of wind-dispersed pollen that trigger hayfever, seasonal asthma and related immune reactions in humans. Up to 25% of adults suffer these allergic responses as a result of inhaling pollen-laden air. (Knox, B. et al., (1996) Trends in Plant Science 1:156-164.) The major and most wide-spread allergenic component of grass pollen are the group I allergens. (Griffith, I., et al, (1991) FEBS Lett. 279:210-215; Perez, M., et al., (1990) J. Biol. Chem. 265:16210-16215; Esch, R. E. et al., (1989) Mol. Immunol. 26:557-561.) These are glycoproteins of about 30 kD that are quickly and profusely released by grass pollen upon hydration; in humans they bind to IgE antibodies to initiate the allergic response. Pollen from grasses contain one or more forms of these allergens, which are named after the source species, e.g. Lol pI is from Lolium perenne (rye grass), Ory sI is from Oryza sativa (rice), etc. Although the immunological aspects of these allergens, especially Lol pI, have been extensively studied, their biological function in the plant is unknown. Nevertheless, high sequence conservation among homologs in divergent grass species implies that they serve a vital biological function. (Xu, H. L., et al., (1995) Gene 164:255-259; Broadwater, A. H., et al., (1993) Gene 131:227-230.)
Recently, Shcherban et al. (Shcherban, T. Y., et al., (1995) Proc. Natl. Acad. Sci. USA, 92:9245-9249) noted that group I pollen allergens have a distant sequence similarity to expansins. Expansins are extracellular proteins that promote plant cell wall enlargement, evidently by disrupting noncovalent bonding between cellulose microfibrils and matrix polymers. (McQueen-Mason, S., et al. (1994) Proc. Natl Acad. Sci. USA 91:6574-6578; McQueen-Mason, S. et al., (1992) Plant Cell 4:1425-1433.) These previously described expansins are referred to in this specification as alpha-expansins. Applicant has now surprisingly discovered that the group I pollen allergens are structurally and functionally related to expansins and that they comprise a second family of expansins, xcex2-expansins.
The present invention relates to xcex2-expansins, including vegetative homologs of xcex2-expansins, compositions thereof and isolated polynucleotides encoding the xcex2-expansins of the invention. Beta-expansins, and polynucleotides encoding -expansins, of the invention may be of natural origin, isolated and purified or recombinatly produced. For purposes of the present invention, a xe2x80x9cvegetative homologxe2x80x9d is defined as a xcex2-expansin which is originally found in any plant part but pollen.
In one aspect, the invention relates to a polypeptide belonging to a class of xcex2-expansins such as, for example, a group I grass pollen allergen and a vegetative xcex2-expansin and compositions thereof.
In another aspect, the invention relates to a polynucleotide encoding the xcex2-expansin of the invention, and a vector, a host cell and a transgenic plant comprising said polynucleotide.
In yet another aspect, the invention relates to a method of altering physical properties of the plant cell wall or any cell wall products derived from plant material, for example paper or textile.
In a further aspect, the invention relates to a method of identifying, isolating and purifying an expansin protein (including both xcex1 and xcex2-expansins) or a polynucleotide encoding such protein.